1. Field of the Invention
This invention relates to equipment for determining the rotational position of a shaft carrying a rotating body and more specifically to rotational-position detecting apparatus which utilizes a noncontact method for determining rotational position.
2. Prior Art
Synchronous resolvers utilizing electromagnetic coupling principles are well known as devices for determining the position of a rotating body. In such devices the coefficient of electromagnetic coupling between a rotor and a stator is a sine or cosine function of the rotational position of the rotating body, as viewed from a reference axis on the stator of the resolver. In such devices the winding of the stator is excited by sine-wave voltage and the output voltage from the rotor is a cosine function of the input sinewave voltage. The problem with such electromagnetic resolvers is that windings are required for both the stator and the rotor and the degree to which the size of the resolver can be reduced is limited by the need for such windings.
Further, an exciting voltage and a demodulation circuit are necessary in order to derive the desired output indicator signal. Such a circuit can be relatively complex. With complexity comes higher cost and greater size.
Therefore, it is a general object of the present invention to provide low-cost, compact, lightweight and inexpensive means for determining the rotational-position of a rotating body.
It is a further object of the present invention to provide, for determining the rotational-position of a rotating body, apparatus which is free of the problems associated with electromagnetic resolvers.